Steps:
1. Downloaded cm-9-20121111-NIGHTLY-galaxys2.zip (verified MD5 checksum cb8a958018247ad62df0d4db4d09d383)
2. Reboot into Recovery and created backup.
3. Flashed cm-9-20121111-NIGHTLY-galaxys2.zip
4. wipe cache partition.
5. advanced > Wipe Dalvik Cache.
6. Reboot.
